1. Field of Invention
The present invention relates to a liquid crystal display device and electronic apparatus. More particularly, the invention relates to a liquid crystal display device which reduces or prevents a connection failure due to the ingress of a conductive material, such as a solder ball, into a cholesteric liquid crystal layer when an electronic component is mounted to be connected to a conductor formed on a substrate having the cholesteric liquid crystal layer.
2. Description of Related Art
Reflective-type liquid crystal display devices can be applied in a variety of mobile electronic apparatus because they do not have a light source, such as a back-light, incorporated therein, and thus they consume less power. Reflective-type liquid crystal display devices take advantage of ambient light, such as natural light or illumination light, but are difficult to view under dark conditions. Liquid crystal display devices have been proposed which use ambient light under light conditions as in an ordinary reflective-type liquid crystal display device, while presenting a display via an internal light source under dark conditions. This type of liquid crystal display device employs a reflective and transmissive display method. Depending on the ambient light level, the device switches between a reflective mode and a transmissive mode. The device presents a distinct display under dark conditions while saving power. In this specification, this type of liquid crystal display device is referred to as a “transflective-type liquid crystal display device.”
In one proposed transflective-type liquid crystal display device, a reflective layer, formed of a metal film such as aluminum or the like and having slits (apertures), to transmit light is arranged on the inner surface of a lower substrate (in this specification, one surface of the substrate facing the liquid crystal is referred to as an “inner surface”, and the other surface of the substrate opposite from the inner surface is referred to as an “outer surface”), and the reflective layer functions as a transflective layer. In this liquid crystal display device, the use of the metal film arranged on the inner surface of the lower substrate controls the parallax of the display device due to the thickness of the lower substrate, and particularly, prevents color mixing if the structure using a color filter is adopted.
FIG. 8 illustrates a related art transflective liquid crystal display device having this type of transflective layer.
The liquid crystal display device 100 includes liquid crystal cells including a liquid crystal 103 encapsulated between a pair of transparent substrates 101 and 102. A reflective layer 104 and an insulator 106 are laminated on the lower substrate 101. Lower electrodes 108, which are electrically conductive transparent layers fabricated of indium tin oxide (hereinafter referred to ITO), are formed on the insulator 106. An alignment layer 107 is formed to cover the lower electrode 108. On the other hand, a color filter 109 having color layers of R (red), G (green), and B (blue) is formed on the upper substrate 102. A planarization layer 111 is laminated on the color filter 109. Upper electrodes 112, fabricated of electrically conductive transparent film such as ITO, are formed on the planarization layer 111. An alignment layer 113 is then deposited to cover the upper electrodes 112 from below.
The reflective layer 104 is fabricated of a metal having a high light reflectance such as aluminum, and has a slit 110 to transmit light for each pixel. Through the slit 110, the reflective layer 104 can function as a transflective layer (hereinafter, the reflective layer 104 is referred to as a “transflective layer”). Arranged on the outer surface of the upper substrate 102 are a forward diffuser 118, a retardation film 119, and an upper polarizer 114 in that order from the upper substrate 102. Arranged on the outer surface of the lower substrate 101 are a ¼-wave plate 115, and a lower polarizer 116 in that order from the lower substrate 101. A backlight 117 (an illumination device) is arranged beneath the lower polarizer 116 below the bottom surface of the lower substrate 101.
When the liquid crystal display device 100 shown in FIG. 8 is used in a reflective mode under light conditions, external light, such as sunlight or illumination light entering from above the upper substrate 102, is transmitted through the liquid crystal 103, is reflected from the surface of the transflective layer 104 on the lower substrate 101, is transmitted through the liquid crystal 103 again, and then exits toward the upper substrate 102. When the liquid crystal display device 100 is used in a transmissive mode under dark conditions, light emitted from the backlight 117 arranged below the lower substrate 101 is passed through the slit 110 of the reflective layer 104, is transmitted through the liquid crystal 103, and then exits toward the upper substrate 102. These light rays contribute to image displaying in each mode.
In the reflective-type liquid crystal display device, a metal film having a high light reflectance, such as aluminum or silver, has been used in the related art for the reflective layer. A dielectric mirror can be formed of dielectric thin films having different refractive indices alternately laminated, a reflective cholesteric plate formed of a cholesteric liquid crystal, or a reflective hologram plate using a hologram element is used for the reflective layer in the reflective-type liquid crystal display device. These reflective plates not only reflect light, but also have other functions.
In particular, the cholesteric liquid crystal exhibits a liquid crystal phase above a certain temperature (liquid crystal transition temperature), in which liquid crystal molecules take a helical structure configuration with a constant pitch. This structure has the property that the cholesteric liquid crystal selectively reflects light having a wavelength coinciding with the helical pitch thereof while transmitting light having other wavelengths. The helical pitch is controlled by the intensity of ultraviolet light or temperature at the curing of the liquid crystal. The color of reflected light is localized, and the cholesteric liquid crystal is thus used as a reflective color filter.
If a plurality of cholesteric liquid crystal layers reflecting light rays of different colors are laminated, the cholesteric liquid crystal functions as a reflective plate that reflects white light.